Battery assisted RFID system RF power control and interference mitigation methods

• US 8,952,788 B1
• Filed: 02/25/2013
• Issued: 02/10/2015
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Intelleflex Corporation
• Inventors: Dacus, Farron, van Niekerk, Johannes Albertus, Rodriguez, Alfonso
• Primary Examiner(s): Syed, Nabil
• Application Number:
  US13/776,504
• Time in Patent Office: 715 Days
• Field of Search: 340/10.1, 340/10.2, 340/10.3, 340/10.31, 340/10.32, 340/10.33, 340/10.34, 340/10.4, 340/10.5, 340/10.51, 340/572.1, 340/572.3, 340/572.7, 340/541, 340/562.2, 455/41.1, 455/41.2
• US Class Current: 340/10.1
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: H04Q 2213/13095 PIN / Access code, authentication

Abstract

A method for controlling RF power within an RFID system according to one embodiment includes returning a first set of RFID tags that were successfully accessed at a first reader forward mode power level to a hibernate state; initiating a timer operation in each of the RFID tags within the first set of RFID tags, the timer operation defining a period of time; and preventing the first set of RFID tags from responding to an activation command at a second reader forward power level during the period of time, the second reader forward power level being higher than the first reader forward power level; and wherein a flag state stored in each of the RFID tags within the first set of RFID tags indicates whether the timer operation is active to prevent undesired activation at the second reader forward power level.

Claims

1. A method for controlling RF power within an RFID system, the method comprising:

sending an activate command to a first set of RFID tags;

returning the first set of RFID tags that were successfully accessed at a first reader forward mode power level to a hibernate state;

initiating a timer operation in each of the RFID tags within the first set of RFID tags including sending a timer value to the first set of RFID tags, the timer operation defining a period of time, wherein the timer value sets the period of time;

preventing the first set of RFID tags from responding to an activation command at a second reader forward power level during the period of time, the second reader forward power level being higher than the first reader forward power level; and

sending a command to the first set of RFID tags to wake up prior to expiration of the period of time defined by the timer operation; and

communicating with the first set of RFID tags,

wherein the activate command includes a field instructing the first RFID tags to set a flag state,

wherein the flag state stored in each of the RFID tags within the first set of RFID tags indicates whether the timer operation is active to prevent undesired activation at the second reader forward power level,

wherein the timer value is selected by an RFID reader based on at least one of;

an expected number of tags and a data rate or data rates used by the RFID reader.

2. The method of claim 1 wherein a reader programmable timer is used to perform the timer operation.

3. The method of claim 1 wherein the command is an activation command, wherein a field in the activation command indicates to the first set of RFID tags to wake up.

4. The method of claim 1 wherein the command is sent at a lower power level than the second reader forward power level.

5. The method of claim 1 wherein the timer value is selected by an RFID reader based on an expected number of tags.

6. The method of claim 1 wherein the timer value is selected by an RFD reader based on a data rate or data rates used by the RFID reader.

7. The method of claim 1 wherein the timer value is selected by an RFID reader based on an amount of information to be read from the RFID tags.

8. The method of claim 1 wherein the timer value is selected by an RFID reader based on a level of interference.

9. The method of claim 1 wherein the timer value is selected by an RFID reader based on time sharing of a radio band used by the RFID reader.

10. The method of claim 1 further comprising:

transmitting a command from an RFID reader, the command having a plurality of fields that communicate information between the RFID reader and a plurality of RFID tags;

wherein the command has a tag receiver sensitivity control field, within the plurality of fields, that sets at least one activated RFID tag, within the plurality of RFD tags, to a particular sensitivity state, the tag receiver sensitivity control field being set by the RFID reader; and

adapting, in the RFID reader, a normal mode forward and reverse transmit power thereof based upon the particular sensitivity state set in the at least one activated RFID tag.

11. The method of claim 10 wherein the RFID reader selects the particular sensitivity state based on a measured interference level in an environment in which communication between the RFID reader and the at least one RFID tag is occurring.